Carambola, commonly known as star fruit, is a fruit produced from the carambola tree (Averrhoa carambola) a native of the East Indies. The carambola tree is a member of the oxalis family (Oxalidaceae) and bears small rose-purple flowers and smooth skinned, ridged, ovate fruit about 4 inches (10 cm) long. The fruit is characterized by a plurality of carinae which are positioned around and extend radially outward from the central body of the fruit defining a plurality of keel-like ridges. Carambola fruit is typically characterized by a five-angled loculicidal capsule. The common name "star fruit" comes from the characteristic shape of the fruit when cut crosswise. A cross section of the fruit reveals the inner fruit material which has a tough, apple-like consistency surrounded by a thick waxy rind-like skin integrally attached to the fruit material. Both the fruit material and the rind-like skin extend outward to form the characteristic star shape.
Worldwide acceptance of the star fruit as an edible and highly nutritious component in human diets has been slow. This is due, in part, to difficulties surrounding preparation of the fruit. The carambola tree itself has a limited growing region requiring tropical or at least subtropical climates. Additionally, the extraction of the fruit from the waxy tough rind-like skin has been difficult. Generally, the star fruit is sectioned and individual surfaces of the five-angled rind-like skin are removed by cutting or paring. This process is extremely time consuming and wasteful of nutritional fruit and flavoring components found proximate to the rind-like skin which is discarded with the parings. The fruit itself is generally eaten raw or is preserved or pickled.
Carambola, like other members of the oxalis family contain an acrid sap-like material composed of oxalic acid in the form of dissolved potassium oxalate. The sap is excreted as calcium oxalate and appears on plant parts as a colored viscous liquid or solid material. The sap acts as a protective device in nature to ward off foragers and the like. Heretofore, it has been believed that the rind-like section was inedible or, at the very least unpalatable. Without being bound to any theory, it is believed that this was due, in part, to the unpleasant granular feel of the rind upon chewing and to the presence of oxalic acid in the rind.
The difficulties in preparation and the heretofore limited growing region have relegated the carambola or star fruit to the role of decorative component in exotic seasonal dishes. However, the star fruit provides edible plant material which is high in nutrients and pleasant tasting. Additionally, if more convenient processing methods can be developed, the carambola could provide a substitute without the drawbacks found in more highly acidic fruits such as citrus fruits and the like; namely acid intolerance, etc.
Because of this, it would be desirable to provide a method for producing a food material which contains as its major component the edible portions of carambola; particularly the desirable juice component of the fruit. It would also be desirable to provide a method which permits the desired components of carambola to be easily removed or isolated from undesirable portions, ideally, in a manner which would permit the use of the nutritional portions of the fruit outside the growing regions for this plant. It is also desirable to provide additional methods for preserving the nutritional value of carambola beyond its typical growing season. Finally, it would be desirable to provide a potable beverage which contains as its major constituent juices derived from carambola or star fruit which would be both nutritious and provide a ready nutritional substitute for individuals desiring or requiring a different juice due to digestive intolerances or allergies experienced with other traditional fruit juices.